One of the known home systems provided with solar cells is an invention described in Patent Literature 1, for example. Patent Literature 1 describes about the following operation. The home system calculates an amount of photovoltaic electricity predicted and an amount of charge predicted for a vehicle's rechargeable battery and supplies the photovoltaic electricity to the vehicle's rechargeable battery if the rechargeable battery needs to be charged. When the amount of photovoltaic electricity predicted is larger than the amount of charge predicted, the home system supplies the surplus electricity to house loads. When the amount of photovoltaic power predicted is larger than the sum of the amount of charge predicted and the house loads, the home system supplies the surplus electricity to a house-side rechargeable battery. When there is still surplus electricity, the home system sells the surplus electricity.
In order to urge effective use of electricity in the house like Patent Literature 1, it is necessary to develop an environment where the user can easily use the vehicle.